Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.85	12.766%	$264.831	$264.83	$264.85	$264.80
Purchase #2	$231.83	9.692%	$254.299	$254.30	$254.30	$254.30
Purchase #3	$125.35	5.554%	$132.3119	$132.31	$132.30	$132.30
Purchase #4	$47.29	13.454%	$53.6524	$53.65	$53.65	$53.70
Purchase #5	$11.72	10.612%	$12.9637	$12.96	$12.95	$13.00
Purchase #6	$162.99	5.563%	$172.0571	$172.06	$172.05	$172.10
Purchase #7	$138.82	3.736%	$144.0063	$144.01	$144.00	$144.00
7 purchase totals =	$952.85		$1,034.1214	$1,034.12	$1,034.10	$1,034.20